1. Field of the Invention
The present invention relates generally to the field of analyzing wear particles in used lubricants. More specifically, the present invention discloses an apparatus for extracting wear particles from a series of used oil filters to create a uniform series of samples for subsequent testing and analysis.
2. Statement of the Problem
A number of systems have been used in the past to monitor engine condition by qualitative or quantitative analysis of wear particles. These systems typically begin by sampling the engine oil. For example, U.S. Pat. No. 3,526,127 to Sarkis discloses a computerized system for automated analysis of a large number of oil samples. Each sample container 1 is first agitated by a shaking station 2. The sample is then passed to a sample recording station 3 wherein sample data (e.g., oil type, engine type, and customer) are entered. The viscosity, infrared characteristics, and metal contents of each sample are measured and analyzed by a computer.
In contrast to the prior art systems, the present invention is designed to extract wear particles trapped within used oil filters. These particles can then be separated according to their size range or magnetic properties and subsequently analyzed qualitatively or quantitatively using a conventional energy dispersive x-ray fluorescence (EDXRF) system. More specifically, the present invention is designed to meet the particular needs of the Joint Oil Analysis Program (JOAP) laboratories. These laboratories belong to the Army, Navy, Air Force, and other Department of Defense (DoD) agencies. All of these laboratories are part of an interagency cooperative effort to implement an effective condition monitoring response to threats, and to increase safety of service personnel and the longevity of the hardware transporting the personnel. It is the responsibility of the JOAP Technical Support Center (TSC) to set the equipment standards for analysis for each of the individual condition monitoring and oil analysis programs operated by the Army, Navy, Air Force, and other DoD agencies.
Several types of jet engines including those used on the F-18 fighter and the Blackhawk, Apache, and Nighthawk helicopters are now using specially designed oil filters rated to pass only particles smaller than 15 microns in size. However, after only a few hours of operation, carbon in the oil creates a fine filter coating on the surface of the oil filter that effectively prevents passage of all particles larger than 0.3 micron. Since all particles larger than 0.3 micron are trapped in the oil filter of the aircraft equipped with the fine filtration, there are no wear metal particles available for analysis in a conventional sample of engine oil. Therefore, conventional monitoring systems based on engine oil samples will provide little meaningful information due to the scarcity of wear particles suspended in the oil samples and may completely fail to recognize dangerous engine conditions.
In addition, there is a growing recognition in the engine condition monitoring field that the larger metal particles (10 microns and up) are far more indicative of abnormal wear and are the best indicators of impending, possibly catastrophic failure. This seems reasonable because small metal particles present in the oil are the result of both normal wear and large particles being ground into small particles by the mechanism. Therefore, any analytical technique that is capable of analyzing only for small particles will be less effective in predicting a need for engine maintenance, and will only occasionally be able to predict the impending catastrophic failures that are most hazardous.
Experimental studies have also been performed in the past using wear particles that have been extracted from used oil filters by manual flushing or rinsing. However, these experimental studies have been subject to sample variation due to differences in the amount of solvent fluid, solvent residence time, and the specific manner in which each oil filter is manually rinsed. The laboratory technician must extensively handle each oil filter and is also exposed to the waste oil and the liquid solvent. In contrast, the present system provides a means to standardize such ad hoc laboratory procedures so that a large number of used oil filters can be tested with a high degree of uniformity. The present system also minimizes the operator's handling of the oil filter and exposure to waste oil and solvent.
Although the present invention was specifically developed to support aircraft engines used for helicopters and jet fighters, it should be expressly understood that the invention is also applicable to analysis of oil filters from commercial aircraft, ground-based equipment such as heavy construction equipment, trucks, power generation stations, ocean liners, other types of ships, and high-performance automobiles. In short, the present system is readily adaptable to all types of machinery equipped with an oil filter designed to trap any form of particulates.
3. Solution to the Problem
None of the prior art references show a system for extracting particles trapped in used oil filters, including over-sized particles and particles trapped by the fine-filtration oil filters currently used in military aircraft. In particular, the present invention provides an automated system for extracting wear particles by rotating the oil filter at high speed while spraying a solvent fluid into the opening at the base of the oil filter.